Photovoltaic (PV) power generation systems can include one or more photovoltaic panels forming a panel array. The panel array is connected to power electronic devices that are used for optimizing the energy capture from the panels and for supplying the generated power to a grid or to energy storages. The power electronic devices can include one or more converter stages for modifying the voltage and/or current obtained from the panel array. The power electronic devices in the PV systems have been referred to as solar inverters or PV inverters although the devices can include other converter topologies than an inverter.
Solar power plants or photovoltaic power generation systems operate in changing environmental conditions. The environmental conditions change seasonally and with the weather. This leads to the fact that the criteria used for setting parameters for the optimal starting conditions are not constant. If a PV generator is started too early in the morning, it will not produce enough power and will be shut down, to be started again later. Such unnecessary starts and shutdowns wear down the components of the power generator system.
On the other hand, if the generator system is started too late, some of the energy is lost; e.g., all possible energy from the solar panels is not fed to the electrical grid.
It is known to optimize the parameters acting as starting criteria for the converters connected to a solar panel system according to changing conditions. Examples of the starting criteria are the voltage from the panel array and the time delay for the start. According to these criteria, the morning start-up procedure includes monitoring the open circuit voltage from the panel array, and when the voltage exceeds a set limit, the solar inverter is started after the time period set by the time delay has expired. In known systems these parameters are corrected manually according to prevailing conditions. The manual setting of parameters for the starting criteria can involve additional work both in the commissioning and during the operation of the solar power plant.
The manual optimization of the parameters further leads to non-optimal situations due to the changing conditions. For example, when the PV panels are covered with dust the power generating system is not able to start with the criteria initially set for clean panels. The same problem occurs when panels or their connections are faulty. Correspondingly, when old panels are replaced with new ones or when panels are serviced, the criteria set for starting are no longer optimal.
It is also known to optimize the starting parameters by using external irradiation or temperature sensors. Such external sensors, however, can add to the complexity and costs of the system. Further, these external sensors cannot take into account changes occurring in the PV panels. Such changes occur, for example, when the panels grow old or dirty.